Comment 28 for bug 321720

Here is more information about the format:

http://en.wikipedia.org/wiki/Acroforms#AcroForms
http://en.wikipedia.org/wiki/XML_Forms_Architecture

pdftk has an option that possibly can be used as a workaround/help:

[drop_xfa]
If your input PDF is a form created using Acrobat 7 or Adobe Designer, then it probably has XFA data. Filling such a form using pdftk yields a PDF with data that fails to display in Acrobat 7 (and 6?). The workaround solution is to remove the form's XFA data, either before you fill the form using pdftk or at the time you fill the form. Using this option causes pdftk to omit the XFA data from the output PDF form.
This option is only useful when running pdftk on a single input PDF. When assembling a PDF from multiple inputs using pdftk, any XFA data in the input is automatically omitted.

From the man page: http://linux.die.net/man/1/pdftk